The present invention relates to a drive system for an electrochromic display containing an electrochromic material held in contact with two electrode carrying support plates, at least one of which is transparent, to manifest reversible variations in the light absorption properties upon current being supplied thereto.
A display containing electrochromic material (referred to as "ECD" hereinbelow) will be summarized in the following paragraph. There are two types of the electrochromic display. See, for example, L. A. Goodman, "Passive Liquid Displays," RCA Report 613258. The first type of ECD includes an inorganic solid film formed on electrodes, which produces color variations by the change in the opacity. The second type of ECD utilizes an electrically induced chemical reduction of a colorless liquid to produce a colored, insoluble film on a cathode surface.
In such ECDs, memory effects are expected, which maintains the coloration state or the bleached state for several hours through several days as long as ECDs are held in an electrically opened state. If electric signals are available indicating whether an ECD is maintained in the coloration state or the bleached state, they would be useful for further utilization such as further data processing.